Event Horizon Telescope spots source of black hole jets

A set of linked radio-telescopes across Hawaii, Arizona and California has given scientists a close-up of the accretion disk of a distant supermassive black hole

The linked dishes, dubbed the Event Horizon Telescope, grabbed the fine details of a supermassive black hole in the M87 galaxy, some 50 million light-years distant, with a mass estimated at 6 billion times that of the Sun.

Their analysis, published in Science (abstract), is based on analyzing the accretion disk surrounding the M87 black hole. The accretion disk, spinning at close to light-speed, is also the source of the jets of matter that typify black hole observations.

The scientists say their observation shows that the accretion disk is just 5.5 times the event horizon of M87 – a size which almost certainly means the M87 black hole is spinning, having received its orbital momentum from the accretion disk.

Were the black hole not spinning, the accretion disk would have to be 7.4 times the Schwartzchild radius, while if the two were spinning in opposite directions, the disk would have to be even larger – more than nine times the event horizon.

MIT researcher Shep Doelman said the observation helps provide confirmation of general relativity in the extreme environments near a black hole. The group, led by MIT’s Haystack Observatory, hopes to scale up in the future by adding dishes in Chile, Europe, Mexico, Greenland and Antarctica. ®

Bootnote: Avid science fiction readers will surely have wondered the same thing as I: isn’t the radius of a black hole possibly infinite? ®